A group of 20 prisoners escaped in January after assaulting a guard and stealing his keys, sparking a review from former Victoria Police chief commissioner Neil Comrie.

His report, released on Friday, says Victoria's youth justice system is not sustainable and needs reform to deal with a significant number of high-risk, violent young offenders.

"Infrastructure, policy and systems that were designed and built for a different era have proven to be incapable of delivering a safe and secure youth justice system in 2016/2017," Mr Comrie said in the review.

All the prisoners were recaptured within 48 hours.

The review found there was an issue with some roller doors, which the escapees were able to breach, but they have since been replaced and strengthened.

Families and Children Minister Jenny Mikakos said work was well under way to improve safety and security at the Malmsbury Youth Justice Centre.